Applicant's own U.S. Pat. No. 7,154,034, incorporated herein by reference, describes a dielectric cutout cover. The cover protects birds and other animals from electrocution, which may also trigger an over-current condition that causes a power outage.
FIGS. 1, 3, and 4 are reproduced from U.S. Pat. No. 7,154,034 and are used to illustrate a problem that has been reported by linemen in the field when opening the fuses using a loadbreak tool.
FIG. 1 illustrates a conventional fuse cutout 10. A mounting bracket 12 secures a ceramic or polymer insulator 14 to a wooden utility pole or cross-arm used to support high voltage conductors, such as carrying 3-phase 12KVAC or higher. A “hot” wire 16 is attached to one phase. A metal connector 18 electrically connects to the wire 16 to a top contact 20 of a blowable fuse 22. The fuse 22 electrically connects to a pivot joint 24 and a bottom connector 26. The bottom connector 26 is connected to another wire (not shown) which may lead to a transformer or any other electrical device or conductor. Opening or blowing of the fuse 22 disconnects the top contact 20 from the bottom connector 26.
A metal hook assembly 28 is fixed to the connector 18 and is used to temporarily support a loadbreak tool for opening the fuse 22 (described with respect to FIG. 2). The bent hook assembly 28 is better shown in FIG. 6. A metal pull ring 30 is physically and electrically connected to the upper end of the fuse 22.
FIG. 2 is a simplified illustration of a portion of a conventional loadbreak tool 34, such as the Loadbuster™ by S&C Electric Company, that is used by linemen to open the fuse 22 while the wire 16 is energized. A description of the well-known Loadbuster™ is found at the web address http://www.sandc.com/en/products--services/products/loadbuster-tool/ and is incorporated herein by reference. A long dielectric pole 35 is affixed to the bottom portion of the loadbreak tool 34 for manipulating the loadbreak tool 34 by the lineman. The diagram of the loadbreak tool 34 is intended to illustrate any loadbreak tool or hotstick used by a lineman that allows the lineman to open and close the fuse 22 while the wire 16 is energized. The loadbreak tool 34 is formed of a dielectric material with two metal hooks that engage the cutout 10, as described below, to allow the lineman to open and close the fuse 22 at a distance to avoid arcing.
The loadbreak tool 34 is positioned by a lineman, while the wire 16 is energized, so that an opening in a metal upper hook 36 of the loadbreak tool 34 is physically and electrically engaged with the metal hook assembly 28 of the cutout 10. Another metal hook 37 at the end of the pole 35 is physically and electrically engaged with the metal pull ring 30, electrically connected to the top of the fuse 22. The metal hook 37 is electrically connected to a loadbreak mechanism internal to the loadbreak tool 34. When the lineman pulls down on the pole 35, the slidable portion 38 is also pulled down. When the pole 35 and slidable portion 38 are pulled down by the lineman, the fuse 22 is pulled away from the top contact 20, and the loadbreak tool 34 creates a parallel circuit (internal to the loadbreak tool 34) that prevents arcing while the fuse 22 is being pulled down. Once the fuse 22 is pulled down a certain distance, a spring in the loadbreak tool 34 rapidly separates contacts within the loadbreak tool 34 to prevent arcing. The loadbreak tool 34 is then removed, and there is an open circuit between the wire 16 and the bottom connector 26.
In a simpler version, the loadbreak tool is simply a stick with a hook that engages the pull ring 30 to allow the linemen to open the fuse 22 when the wire 16 is energized.
FIGS. 3 and 4 illustrate a dielectric cover 44 previously invented by the Applicant. FIG. 4 shows the cutout 10 mounted to a wooden utility pole 46. The cutout 10 may instead be mounting on a wooden cross-arm of the utility pole 46. The pull ring 30 always faces away from the pole or cross-arm. The cover 44 also represents a similar design of other commercially available cutout covers that have a slot 46 in the back for placing the cover 44 over the cutout 10, and removing the cover 44 from the cutout 10, while the energized wire 16 is connected. In some covers, the slot may resiliently close after the wire 16 passes through. The cover 44 covers the entire cutout 10, including surrounding the metal hook assembly 28 and the pull ring 30 on their lateral sides. A flared-out portion of the cover 44 is intended to allow easy access to the hook assembly 28 and pull ring 30 by the loadbreak tool 34. However, it has been reported by linemen that, at certain wide angles, such as greater than about 20-30 degrees relative to vertical, the sidewalls of the flared portion of the cover 44 prevent the loadbreak tool 34 from hooking onto the hook assembly 28 and the pull ring 30. Sometimes, access to the cutout 10 or positioning by the lineman relative to the cutout 10 is limited, and the lineman needs to position the loadbreak tool 34, relative to the cutout 10, at a wider variety of engagement angles.
Simply widening the flared portion of the cover 44 would allow access over a wider range of angles, but wind forces on the open areas of the cover 44 would greatly increase and may result in the cover 44 being blown off or damaged. Additionally, widening the flared portion would invite animals, such as squirrels and birds, to nest in the wider opening, increasing the chances of a short to ground. It has been brought to the Applicant's attention that squirrels sometimes completely fill the flared opening with acorns.
Hubbell Power Systems, Inc. offers a cutout cover model CC101 that snaps over the insulator and provides a rounded shroud roof over the pull ring 30 and hook assembly 28. A website address for the cover is https://www.reynoldsonline.com/ASSETS/DOCUMENTS/ITEMS/EN/HUPOGS560_Spec.pdf. One problem with such a design is that the top of the loadbreak tool 34 must get under the rounded shroud roof and may hit the inner or outer opposing walls of the rounded shroud when manipulating the loadbreak tool 34. This limits the angles that the lineman may position the loadbreak tool 34 relative to the cutout. Further, since the Hubbell cover is secured in place by resiliently snapping it into place over the insulator, the size of the cover must be precisely tailored to a particular type of insulator. Further, it is difficult to remove the cover using a hotstick. Still further, since the Hubbell cover overlaps the top skirt of the insulator, contamination and moisture on the cover may cause a leakage current to flow across the surface of the cover, reducing the effective insulation.
What is needed is an improved cutout cover that enables a lineman to engage the cutout with a conventional loadbreak tool or hotstick over a wider range of angles, while the cover still provides an insulating barrier to energized parts.